KUALA LUMPUR, Malaysia — Vietnamese searchers on ships worked throughout the
night but could not find a rectangle object spotted Sunday afternoon
that was thought to be one of the doors of a Malaysia Airlines passenger
jet that went missing more than two days ago.

Doan
Huu Gia, the chief of Vietnam's search and rescue coordination center,
said Monday that four planes and seven ships from Vietnam were searching
for the object but nothing had been found.

The Boeing 777 went missing early Saturday morning on a flight from Kuala Lumpur to Beijing with 239 people on board.

The
plane lost contact with ground controllers somewhere between Malaysia
and Vietnam, and searchers in a low-flying plane spotted an object that
appeared to be one of the plane's doors, the state-run Thanh Nien
newspaper said, citing the deputy chief of staff of Vietnam's army, Lt.
Gen. Vo Van Tuan.

The jetliner apparently fell
from the sky at cruising altitude in fine weather, and the pilots were
either unable or had no time to send a distress signal, adding to the
mystery over the final minutes of the flight.

There are also questions over how two passengers managed to board the ill-fated aircraft using stolen passports.

Interpol
confirmed it knew about the stolen passports but said no authorities
checked its vast databases on stolen documents before the Boeing
jetliner departed Saturday.

Warning "only a
handful of countries" routinely make such checks, Interpol secretary
general Ronald Noble chided authorities for "waiting for a tragedy to
put prudent security measures in place at borders and boarding gates."

On
Saturday, the foreign ministries in Italy and Austria said the names of
two citizens listed on the flight's manifest matched the names on two
passports reported stolen in Thailand.

"I can
confirm that we have the visuals of these two people on CCTV," Malaysian
Transport Minister Hishammuddin Hussein said at a news conference late
Sunday, adding that the footage was being examined. "We have
intelligence agencies, both local and international, on board."

The
thefts of the two passports - one belonging to Austrian Christian Kozel
and the other to Luigi Maraldi of Italy - were entered into Interpol's
database after they were stolen in Thailand in 2012 and last year, the
police body said.

Electronic booking records
show that one-way tickets with those names were issued Thursday from a
travel agency in the beach resort of Pattaya in eastern Thailand. A
person who answered the phone at the agency said she could not comment.

But
no authorities in Malaysia or elsewhere checked the passports against
the database of 40 million stolen or lost travel documents before the
Malaysian Airlines plane took off.

Possible
causes of the crash included some sort of explosion, a catastrophic
failure of the plane's engines, extreme turbulence, or pilot error or
even suicide. Establishing what happened with any certainty will need
data from flight recorders and a detailed examination of any debris,
something that will take months if not years.

Malaysia's
air force chief, Rodzali Daud, said radar indicated that before it
disappeared, the plane may have turned back, but there were no further
details on which direction it went or how far it veered off course.

"We
are trying to make sense of this," Daud said at a news conference. "The
military radar indicated that the aircraft may have made a turn back,
and in some parts this was corroborated by civilian radar."

Malaysia
Airlines Chief Executive Ahmad Jauhari Yahya said pilots are supposed
to inform the airline and traffic control authorities if the plane does a
U-turn. "From what we have, there was no such distress signal or
distress call per se, so we are equally puzzled," he said.

A
total of 34 aircraft and 40 ships from Vietnam, Malaysia, Thailand,
Australia, Singapore, Indonesia, China and the United States were
deployed to the area where ground controllers lost contact with the
plane on the maritime border between Malaysia and Vietnam.

Of
the 227 passengers and 12 crew members on board, two-thirds were
Chinese, while the rest were from elsewhere in Asia, Europe and North
America, including three Americans.

Family
members of former Keller resident Philip Wood, a 50-year-old IBM executive who was on board the
plane, said they saw him a week ago when he visited them in North Texas after
relocating to Kuala Lumpur from Beijing, where he had worked for two
years.

The other two Americans were identified
on the passenger manifest as 4-year-old Nicole Meng and 2-year-old Yan
Zhang. It was not known with whom they were traveling.

After
more than 30 hours without contact with the aircraft, Malaysia Airlines
told family members they should "prepare themselves for the worst,"
Hugh Dunleavy, the commercial director for the airline, told reporters.

Finding
traces of an aircraft that disappears over sea can take days or longer,
even with a sustained search effort. Depending on the circumstances of
the crash, wreckage can be scattered over a large area. If the plane
enters the water before breaking up, there can be relatively little
debris.

A team of American experts was en
route to Asia to be ready to assist in the investigation into the crash.
The team includes accident investigators from the National
Transportation Safety Board, as well as technical experts from the
Federal Aviation Administration and Boeing, the safety board said in a
statement.

Malaysia Airlines has a good safety
record, as does the 777, which had not had a fatal crash in its 19-year
history until an Asiana Airlines plane crashed last July in San
Francisco, killing three passengers, all Chinese teenagers.

Details also emerged Sunday about the itineraries of the two passengers traveling on the stolen passports.

A
telephone operator on a China-based KLM hotline confirmed Sunday that
passengers named Maraldi and Kozel had been booked on one-way tickets on
the same KLM flight, flying from Beijing to Amsterdam on Saturday.
Maraldi was to fly on to Copenhagen, Denmark, and Kozel to Frankfurt,
Germany.

She said the pair booked the tickets through China Southern Airlines, but she had no information on where they bought them.

As holders of EU passports with onward flights to Europe, the passengers would not have needed visas for China.

Interpol
said it and national investigators were working to determine the true
identities of those who used the stolen passports to board the flight.
White House Deputy National Security Adviser Tony Blinken said the U.S.
was looking into the stolen passports, but that investigators had
reached no conclusions.

Interpol has long
sounded the alarm that growing international travel has underpinned a
new market for identity theft: Bogus passports are mostly used by
illegal immigrants, but also pretty much anyone looking to travel
unnoticed such as drug runners or terrorists. More than 1 billion times
last year, travelers boarded planes without their passports being
checked against Interpol's database of 40 million stolen or lost travel
documents, the police agency said.

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